ls-files: don't try to prune an empty index

Exit early when asked to prune an index that contains no entries to
begin with.  This avoids pointer arithmetic on istate->cache, which is
possibly NULL in that case.

Found with Clang's UBSan.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/ls-files.c b/builtin/ls-files.c
index dc4a6aa3d951b46220dcb084d3f86ca7a4cc1a29..c6126eae550beb75e7c90094be337efbb48cd3bc 100644 (file)
--- a/builtin/ls-files.c
+++ b/builtin/ls-files.c
@@ -362,7 +362,7 @@ static void prune_index(struct index_state *istate,
        int pos;
        unsigned int first, last;
 
-       if (!prefix)
+       if (!prefix || !istate->cache_nr)
                return;
        pos = index_name_pos(istate, prefix, prefixlen);
        if (pos < 0)